It could be used as a dog kennel for the right size dog (s), lifting your dog up there. A cat might get there on their own. I always read about people wanting "Pet Space". That would be their own, happy to see around being up high and you happy to have some walking room. Cat or dog (pending size), there should still be some decent space for bulk storage.
I know there are women out there who travel the country quilting and such. They love the over-head bed area of most motor homes for their light weight bulk.
I am trying to get the dimensions from the seller to see how big a child it can accommodate.